The present invention relates to imaging apparatus and in particular to apparatus capable of providing optically sectioned images that may be overlaid to form a three dimensional image. The present invention is particularly suited, but not exclusively, to endoscopy applications employing a fiber optic bundle.
A conventional fiber optic endoscope consists of a fiber optic bundle that is inserted into a human or animal body to the object to be imaged. The end of the fiber optic bundle outside of the body is usually connected to a camera whereas the opposite end of the fiber optic bundle inside the body has a light source that illuminates the site of interest. Scattered light from the object is imaged onto the end of the fiber optic bundle and is guided along the bundle to the camera. The image received by the camera is a conventional image with no depth information other than that obtainable from a simple lens system. Hence, the conventional endoscope is unable to provide optically sectioned images that might be used to create three dimensional images of the object inside the body. Moreover, the light source is usually located inside the body adjacent the object because difficulties arise with back reflections from the end of the optical fibers when the light is transmitted to the site of interest along the fiber optic bundle from the outside.
The present invention seeks to provide an imaging system that is arranged to provide optically sectioned images using a bundle of small light conduits such as optical fibers.
The present invention provides imaging apparatus comprising a first light source; a bundle of light conduits along which light from the first light source passes; a second light source; a lens system for focussing light from the bundle of light conduits onto a specimen and for focussing light scattered from the specimen back to the bundle of light conduits; and an analyzer for extracting an optically sectioned image of the specimen from first and second images of the specimen, the first image being of the specimen illuminated by the first light source and the second image being of the specimen illuminated using the second light source.
Preferably, the bundle of light conduits is a fiber optic bundle.
In a first embodiment of the present invention the first light source is positioned at a first end of the fiber optic bundle and the second light source is positioned at the opposite second end of the fiber optic bundle near to the specimen. Ideally, a beam splitter is provided between the end of the fiber optic bundle and the lens system whereby light from the second light source is introduced into the path of light emerging from the fiber optic bundle.
In an alternative embodiment of the present invention the optical fibers of the bundle are encased in a cladding medium and light from the first light source is coupled to the cladding medium. A prism may be provided for coupling light from the first light source with the cladding medium. Alternatively, the cladding medium may include an integral grating for coupling light from the first light source with the cladding medium. With this embodiment the second light source may be located at either the first or the second end of the fiber optic bundle.
Preferably, the first and second light sources provide substantially identical illumination of the specimen.
In an alternative aspect the present invention provides an adapter for a microscope having a light source and lens system including an objective lens, the adapter comprising a bundle of light conduits along which light from the microscope passes and a second light source, the bundle of light conduits and the second light source being positioned between the microscope light source and the objective lens whereby optically sectioned images of a specimen are extracted from first and second images of the specimen, the first image being of the specimen illuminated by the adapter light source and the second image being of the specimen illuminated using the microscope light source.